Siemens SIMATIC NET PROFIBUS - Manual (Page 486)

Glossary
Glossary-6
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000
SIMATIC NET PC modules
SIMATIC NET PC modules are modules for coupling the PC to bus systems,
such as PROFIBUS or Industrial Ethernet.
Slave
A slave can only exchange data with a ³ master after it has been request to
send data by the master.
Slaves include, for example, all DP slaves such as ET 200S, ET 200X, etc.
SOFTNET for PROFIBUS
SOFTNET for PROFIBUS is the protocol software for the SIMATIC NET PC mo-
dules CP 5511 and CP 5611.
Standard rail
Metal rail standardized in compliance with EN 50 022.
The standard rail is used for the snap-on installation of network components
such as OLMs, repeaters etc.
Suppressor
Component for reducing induced voltages. Induced voltages occur when circuits
with inductances are turned off.
Surge arresters
are used to limit overvoltages from remote strikes or from induction effects (for
example switching in power circuits). Surge arresters (in contrast to lightning ar-
resters) divert currents with a significantly lower peak value, discharges and spe-
cific energies.
Terminating resistor
A resistor to terminate the LAN cable; terminating resistors are always necessary
at the ends of the cable or segment.
In SIMATIC NET PROFIBUS, terminating resistors are activated or deactivated
in the
³
bus connector or bus terminal or are installed as
³
terminators.
Terminator
A ³ terminating resistor in bus segments at transmission rates of 9.6 Kbps to 12
Mbps; the power supply is separate from the bus nodes.
Token
is a frame that represents the right to transmit in a network. It signals the two
states ”occupied” or ”free”. The token is passed from master to master.